Forsterite Research Articles

Injectable gellan gum/lignocellulose nanofibrils hydrogels enriched with melatonin loaded forsterite nanoparticles for cartilage tissue engineering: Fabrication, characterization and cell culture studies

Injectable hydrogels based on natural polysaccharides have attracted considerable attention in cartilage tissue engineering, especially those reinforced with mineral nanofilers carrying drug molecules. Here, a novel injectable hydrogel based on gellan gum (GG)/lignocellulose nanofibrils (LGNF) composite enriched with melatonin (MEL) loaded forsterite (FS) nanoparticles (FS-MEL) was developed to yield enhanced mechanical and biological properties of the hydrogels. Gelation time and temperature were determined for different hydrogel formulation containing 1-5w/v% LGNF and 0.1-0.3w/v% FS-MEL. The injectability test proved the ease of injection of the developed hydrogels. Degradation rate and swelling degree of developed hydrogel were evaluated to determine the effect of LGNF and FS on hydrogel behaviour. Results of mechanical characterization showed that the compressive modulus and strength of GG hydrogels were improved by incorporation of LGNF and FS. The results of MEL release study in PBS revealed that MEL showed more sustained release from the hydrogel compared to FS nanoparticles. Cell-hydrogels interaction was evaluated by culturing chondrocyte cells. Results exhibited higher cell adhesion, proliferation and gene expression on GG/LGNF/FS-MEL hydrogel compared to GG/LGNF and GG/LGNF/FS, which can be attributed to the synergic effect of FS and MEL. Overall results demonstrated that the developed GG/LGNF/FS-MEL hydrogels can be offered as promising materials for cartilage regeneration applications.

Melting of fluorphlogopite-plagioclase pairs at 1 atmosphere

Melting experiments on fluorphlogopite + plagioclase (An68) pairs have been performed at 1 atmosphere, as a function of temperature and run duration. Run products include, in addition to melt, spinel, forsterite and a newly formed calcic plagioclase. The solidus was located between 1100 and 1150°C and the amount of melt produced increases sharply at 1200°C. From this temperature, liquids are compositionally zoned between the two mineral interfaces, and the mica reacts out after sufficient time indicating the existence of a critical temperature of melting located between 1175 and 1200°C. These two temperature domains are also characterized by differences in plagioclase reaction textures, melt proportions and reaction rates. Textural and Sr isotopic studies of the plagioclases show that at all temperatures the first step of the melting reaction is characterized by congruent dissolution of the starting plagioclase followed by precipitation of the new plagioclase. At all temperatures the melt compositions are initially located on the intersection of the cotectic line and the starting plagioclase-fluorphlogopite tie-line. Below the critical temperature of melting these melts are metastable undercooled liquids. Above the critical temperature of melting there is an array of stable melt compositions located on the plagioclase- fluorphlogopite tie-line. In both cases the melt compositions evolve with time toward more albite-rich compositions in conjunction with the new plagioclase precipitation. The system fluorphlogopite-plagioclase thus provides an example where liquid compositions vary with time although plagioclase-melt interface equilibrium is satisfied. This is due to the involvement of a solid solution in the reaction. Above the critical temperature of melting, the rate-controlling process for melting is chemical diffusion in the melt. Below the critical temperature of melting the rate-limiting step is the formation of the metastable undercooled melt. The sluggishness of the melting reaction in this temperature regime is explained by the difficulty of forming such a melt.

Preliminary physicochemical evaluation of kushta-e-zahar mohra: A unique formulation of unani medicine

Introduction: Zahar Mohra (Serpentine/Bezoar stone) is mentioned as efficacious and a useful drug indicated in heart diseases in Unani medicine. It is also used to remove effect of poison and is termed in Unani Medicine as Daf-e-Zahar or Fad-e-Zahar (antidote). It acts as preservative of quwa (faculty) and ruh (pneuma). Unani physicians commonly use Zahar Mohra (ZM) in Kushta (Calcined) form, because the Kushta gives quick and potent response. In this work owing to its beneficial and efficacious use, Kushta-e-Zahar Mohra (KZM) was prepared as per contemporary methods and was subjected to preliminary physicochemical analysis to develop a standard. Materials and Methods: KZM was prepared as per contemporary method (Muffle furnace) by simulation of the heat pattern as per classical texts/method and its physico-chemical and instrumental analysis including XRD, ICP-MS and AAS was performed. Statistical analysis used was Mean ± SEM. Results: Prepared Kushta passes the classical Unani specification tests, contemporary test data for various physicochemical parameters were also set in. XRD analysis indicated presence of Mg2Si O4 (Magnesium Silicate) and Ca (Cl O)2. 3H2O (Calcium Chlorite Hydrate) phase. Conclusions: The study indicates content and physicochemical standards of KZM prepared by contemporary method; it can be a better choice. KZM can be safe for use as acclaimed for heart diseases in Unani System of Medicine.

A Simple but Effective Device to Avoid Objective Lens Overheating: An Air Blower Device

The interior of the Earth is a high temperature and high pressure environment. High temperatures cause important changes in the physical and chemical properties of minerals. An increase in temperature leads to significant changes in the molecular and lattice vibrations, elasticity, and seismic velocity of minerals. The high temperature vibrational spectroscopy (infrared and Raman) used to study these changes can provide highly significant understanding of the Earth’s interior. During high temperature spectroscopy, the heating device that is used to heat the sample can work at a very high temperature (e.g., 1 500 ℃) because it has a cooling device surrounding it that is used to prevent the temperature of its environments from getting too high. However, radiation from its heating elements is intense and this will shine on and heat the objective lens of the focusing system for the spectroscopic light source, and this would result in damage to the lens. Thus, to avoid damage to the objective lens, an upper limit is placed on the heater temperature. The significance of this work is that it presents a method to exceed the present instrument’s temperature limit so that we can perform in situ spectroscopy on samples at higher temperatures. This work extended the temperature limit for the sample to a higher temperature by using an air blower around the objective lens to create a gas flow around it. The gas flow serves to remove heat from the objective lens by forced convection and its turbulent flow also served to increase the rate of heat transport from the lens to the moving gas stream, which together prevented overheating of the objective lens. Our results have shown that although this device is simple, it was highly effective: for a sample temperature of 1 000 ℃, the objective lens temperature was reduced from ～235 to ～68 ℃. Using this device, we performed in situ high temperature Raman spectroscopy of forsterite up to a sample temperature of 1 300 ℃. The results agreed well with previous studies and demonstrated that with our simple air blower device, we can perform in situ high temperature spectroscopy up to 1 300 ℃ without damaging the objective lens and without expensive components like a high temperature composite objective lens or a long focus objective lens.

Metastable structural transformations and pressure-induced amorphization in natural (Mg,Fe)2SiO4olivine under static compression: A Raman spectroscopic study

Raman spectroscopic data were obtained for (Mg,Fe)2SiO4 samples during compression to 57 GPa. Single crystals of San Carlos olivine compressed hydrostatically above 41 GPa showed appearance of a new “defect” peak in the 820–840 cm−1 region associated with SiOSi linkages appearing between adjacent Embedded Image tetrahedra to result in five- or sixfold-coordinated silicate species. Appearance of this feature is accompanied by a broad amorphous background. The changes occur at lower pressure than metastable crystalline transitions of end-member Mg2SiO4 forsterite (Fo-I) into Fo-II and Fo-III phases described recently. We complemented our experimental study using density functional theory (DFT) calculations and anisotropic ion molecular dynamics (AIMD) simulations to study the Raman spectra and vibrational density of states (VDOS) of metastably compressed Mg2SiO4 olivine, Fo-II and Fo-III, and quenched melts at high and low pressures. By 54 GPa all sharp crystalline peaks disappeared from observed Raman spectra indicating complete pressure-induced amorphization (PIA). The amorphous (Mg,Fe)2SiO4 spectrum contains Si-O stretching bands at lower wavenumber than expected for Embedded Image indicating high coordination of the silicate units. The amorphous spectrum persisted on decompression to ambient conditions but with evidence for reappearance of tetrahedrally coordinated units. Non-hydrostatic compression of polycrystalline olivine samples showed similar appearance of the defect feature and broad amorphous features between 43–44 GPa. Both increased in intensity as the sample was left at pressure overnight but they disappeared during decompression below 17 GPa with recovery of the starting olivine Raman signature. A hydrated San Carlos olivine sample containing 75–150 ppm OH was also studied. Significant broadening of the Embedded Image stretching peaks was observed above 43 GPa but without immediate appearance of the defect or broad amorphous features. However, both of these characteristics emerged after leaving the sample at 47 GPa overnight followed by complete amorphization that occurred upon subsequent pressurization to 54 GPa. During decompression the high-density amorphous spectrum was retained to 3 GPa but on final pressure release a spectrum similar to thermally quenched low-pressure olivine glass containing isolated Embedded Image groups was obtained. Leaving this sample overnight resulted in recrystallization of olivine. Our experimental data provide new insights into the metastable structural transformations and relaxation behavior of olivine samples including material recovered from meteorites and laboratory shock experiments.

Wettability between liquid iron and tundish lining refractory

In the current study, the wettability between liquid iron and lining refractory of a continuous casting tundish was investigated. In the sample preparation process, liquid phase was generated during sintering, and CaMgSiO4 and Mg2 SiO4 were precipitated during cooling. The phase transition from solid state to liquid state during the measurement of contact angle lead to the increase of surface roughness. The increase of surface roughness contributed to the increase of contact angle in a short interval. A bigger contact angle would be achieved on a rougher surface. The contact angle between liquid iron and refractory substrates with relatively rough surface was approximately 112.6° at 1550 °C and 107.7° at 1626 °C. When the pure iron melted and covered the surface of substrate, open pores on the surface were not filled by the liquid iron. At the three-phase contact line in the pore, there existed a local contact angle. The average value of the local contact angle was 113.3°, which was close to the measured macro-contact angle. In the second phase rich area, liquid iron penetrated into substrate through pores, the average penetration depth was approximately 140 μ m.

First-principle modelling of forsterite surface properties: Accuracy of methods and basis sets.

The seven main crystal surfaces of forsterite (Mg2 SiO4 ) were modeled using various Gaussian-type basis sets, and several formulations for the exchange-correlation functional within the density functional theory (DFT). The recently developed pob-TZVP basis set provides the best results for all properties that are strongly dependent on the accuracy of the wavefunction. Convergence on the structure and on the basis set superposition error-corrected surface energy can be reached also with poorer basis sets. The effect of adopting different DFT functionals was assessed. All functionals give the same stability order for the various surfaces. Surfaces do not exhibit any major structural differences when optimized with different functionals, except for higher energy orientations where major rearrangements occur around the Mg sites at the surface or subsurface. When dispersions are not accounted for, all functionals provide similar surface energies. The inclusion of empirical dispersions raises the energy of all surfaces by a nearly systematic value proportional to the scaling factor s of the dispersion formulation. An estimation for the surface energy is provided through adopting C6 coefficients that are more suitable than the standard ones to describe O-O interactions in minerals. A 2 × 2 supercell of the most stable surface (010) was optimized. No surface reconstruction was observed. The resulting structure and surface energy show no difference with respect to those obtained when using the primitive cell. This result validates the (010) surface model here adopted, that will serve as a reference for future studies on adsorption and reactivity of water and carbon dioxide at this interface.

Low-Temperature Sintering and Microwave Dielectric Properties of CaWO<sub>4</sub>-Mg<sub>2</sub>SiO<sub>4 </sub>Ceramics

The effect of V2O5addition on the microstructures and the microwave dielectric properties of 0.9CaWO4-0.1Mg2SiO4(9CWMS) ceramics prepared by conventional solid-state routes have been investigated. The V2O5were selected as liquid phase sintering aids to lower the sintering temperature of 9CWMS ceramics. A small amount of V2O5(0.25~1 wt%) were used for sintering aid and led to high densification at 1050°C. The dielectric properties of 9CWMS ceramics with V2O5additions are strongly dependent on the densification, the microstructure. As the amount of V2O5additives increased from 0.25 to 1.0 wt%, the dielectric constantsεrdecreased following the trend with density. The quality valuesQdecreased with the increase of V2O5amount for all sintering temperatures. The 0.25 wt% V2O5-doped 0.9CaWO4-0.1Mg2SiO4ceramicssintered at 1080°C for 2 h had the optimum dielectric properties: εr= 5.7;Q×f= 73000 (at 14 GHz).

Ultrahigh-pressure (UHP) associations in ultramafites of the Maksutov complex (Southern Urals)

or irregular form bodies from 2-3 to 20-30 m in size, which are located mainly in contact zones between eclogites and the surrounding quartzites and schists. Olivine-enstatite and enstatite rocks have yellowish gray or greenish gray color, giantgrained or coarse� grained texture, and starlike structure. Enstatite occurs as rosettes or single elongated crystals in the matrix, made of finegrained forsterite and magnesite. Schistic rocks are surrounded by rims composed of the following associations: talk + phengite, talk + tremo� lite ± winchite (asbestoslike), tremolite + chlorite ± garnet, and others. The rocks are composed of forster� ite, enstatite, magnesite, and clinohumite. Ore minerals are chromite and pentlandite; secondary minerals are serpentine and chlorite (Table 1). Forsterite contains 11-17% of fayalite molecule, which is typical of for� sterite of the Fe-Ti type from olivine peridotites. According to some peculiarities of its chemical com� position (Mg content (0.89-0.91), a higher content of Al (1.86-2.87 wt%), and Ni (up to 0.20 wt%)), enstatite is close to the theoretical composition. Mag� nesite makes up to 25% of the total volume of the sam� ple. The characteristic peculiarity of the magnesite composition is a low Fe and Ca content in olivine- enstatite and enstatite rocks (4.3 and 3.8 wt%, 0.19 and 0.11 wt %, respectively). Titanoclinohumite occurs as small grains in a ser� pentine or magnesite matrix and contains Ti (4.1- 4.5 wt %) and Ni (0.18-0.75 wt %) with insignificant variations in the Mg content (0.88-0.90). Antigorite is characterized by a high Mg content (0.89-0.95) and Cr content, varying from 0.5 to 1.9 wt%. Magnesial chlorite ( ~0.94) has up to 2.5 wt% Cr and 0.6 wt% Ni. Chromite and pentlandite occur as irregular grains in forsterite. The paragenesis of Fo-En-Mgs-Ti-Chu makes it possible to clarify the conditions of formation of the rocks considered. This mineral association is typical of ultramafic rocks of the Dabie Suite and Dabie Shau ultrahighpressure complexes and diamondcontent "calcsilicate" rocks of the Kokchetav massif (3, 5, 8). The experimental data for the CaO-MgO-SiO 2 -

Theoretical infrared spectrum of OH-defects in forsterite

Theoretical infrared spectrum of OH-defects in forsterite

Sol–gel synthesis of forsterite nanopowders with narrow particle size distribution

Forsterite (FS) nanopowders (∼27 nm) were synthesized using a sol–gel route with magnesium nitrate hexahydrate and tetra ethyl ortho-silicate as magnesium and silicon precursors, respectively. Nitric acid was used as a catalyst. After aging, the FS gel was calcined at 800 °C for 30 min. The calcined powders were characterized for phase composition using X-ray diffractrometry and fourier transform-infrared spectroscopy. The particle size and morphology was studied using transmission electron microscopy. The particle size distribution analysis of FS powders showed skewed distribution plot with particle size ranging from 5–90 nm. This study showed that high phase purity and narrowly distributed FS nanoparticles could be obtained using this simple sol–gel technique.

Microstructure–Dielectric Properties Relationship in Ba0.6Sr0.4TiO3–Mg2SiO4–Al2O3 Composite Ceramics

0.60Ba0.6Sr0.4TiO3(BST)–(0.40−x)Mg2SiO4(MS)–xAl2O3 (x=0, 0.5, 3, 5wt%) composite ceramics exhibit excellent characteristics suitable for tunable device applications. With increasing amount of Al, the dielectric peak can be quantitatively broadened and suppressed; the “phase transition temperature”Tc or (Tm) shifts to a lower temperature. Meanwhile, the tunability is still high in a wider temperature range. Far from Tc, pyroelectric effects are observed by using the Byer and Roundy technology and Slim polarization hysteresis loops are observed under high ac dielectric field at 10Hz. These proved the existence of spontaneous polarization in certain possible orientations in a broad temperature range above Tc in the paraelectric medium and reveal why 0.60BST–(0.40−x)MS–xAl2O3 have such remarkable dielectric nonlinearity.

Forsterite exposure causes less oxidative DNA damage and lung injury than chrysotile exposure in rats

Chrysotile (CH) is a pathogenic waste building material that can potentially be rendered innocuous via conversion to forsterite (FO) by heating at high temperatures. We compared the ability of FO and CH to cause oxidative DNA damage and lung injury. A single 1-mg intratracheal dose of CH or FO was administered to rats. Significant changes were observed 3 to 7 days after CH injection in alveolar macrophages, neutrophils, eosinophils, lymphocytes, total protein, and lactate dehydrogenase. High concentrations of 8-hydroxy-29-deoxyguanosine (8-OHdG) were also observed in the macrophages, other infiltrating inflammatory cells, granulomas, and in bronchiolar and alveolar epithelial cells. The overexpression of 8-OHdG was limited to airway epithelial and inflammatory cells surrounding the fibrotic foci 540 days after injection, indicating that the inflammatory effects of CH were persistent yet decreased with time. Compared to the CH group, acute lung inflammation observed in the FO group was less apparent and exhibited no progressive fibrosing lesions. The expression of 8-OHdG was transient and weak in the bronchiolar epithelial cells as well as in the inflammatory cells, consistent with low concentrations of 8-OHdG observed in the lungs. These findings confirm that FO causes significantly less inflammation and oxidative DNA damage in the lungs than CH.

In vitro Degradation, Bioactivity, and Cytocompatibility of Calcium Silicate, Dimagnesium Silicate, and Tricalcium Phosphate Bioceramics

CaSiO3 (CS) ceramics have been regarded as a potential bioactive material for bone regeneration. Mg2SiO4 (M2S) ceramic has been reported as a novel bioceramic with higher mechanical properties and good biocompatibility recently. beta-Ca2(PO4)2 (beta-TCP) ceramic is a well-known bioactive and degradable material for bone repair. The aim of this study is to investigate and compare the effect of three bioceramics with different chemical composition on the in vitro degradation, apatite-forming ability in simulated body fluid (SBF) and cytocompatibility. The degradation was evaluated through the activation energy of Si or P ion released from ceramics and the weight loss of the ceramics in Tris-HCl buffer solution. Formation of bone-like apatite on different bioceramic surfaces was investigated in SBF. The presence of bone-like apatite layer on the material surface after soaking in SBF was demonstrated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM). The effect of ionic products from the three kinds of material dissolution on osteoblast-like cell proliferation was investigated. The results showed that the degradation rate of CS was much faster than that of beta-TCP and M2S ceramics. Apatite formation occurred on the CS ceramics quickly. However, it was less likely to occur on the surfaces of beta-TCP and M2S ceramics. The ionic products from extracts of CS and M2S could stimulate osteoblast-like cell proliferation at certain concentration range throughout the 6-day culture period.

Electron density distribution and bond critical point properties for forsterite, Mg2 SiO4, determined with synchrotron single crystal X-ray diffraction data

A generalized X-ray scattering factor model experimental electron density distribution has been generated for the orthosilicate forsterite, using an essentially extinction and absorption free set of single crystal diffraction data recorded with intense, high energy synchrotron X-ray radiation (E=100.6 keV). A refinement of the model converged with an R(F)=0.0061. An evaluation of the bond critical point, bcp, properties of the distribution at the (3, −1) stationary points for the SiO and MgO bonded interactions, yielded values that agree typically within ~5%, on average, with theoretical values generated with quantum chemical computational strategies, using relatively robust basis sets. On the basis of this result, the modeling of the experimental distribution is considered to be adequate. As the bcp properties increase in magnitude, the MgO and SiO bonds decrease in length as calculated for a number of rock forming silicates. As asserted by Coppens (X-ray charge densities and chemical bonding. Oxford University Press, Oxford, 1997), large negative ∇2ρ(r c ) values, characteristic of shared interactions involving first row atoms, may not be characteristic of closed shell covalent bonded interactions involving second row Si, P and S atoms bonded to O. This study adds new evidence to the overall relatively good agreement between theoretical bcp properties generated with computational quantum strategies, on the one hand, and experimental properties generated with single crystal high energy synchrotron diffraction data on the other. The similarity of results not only provides a basis for using computational strategies for studying and modeling structures, defects and the reactivity of representative structures, but it also provides a basis for improving our understanding of the crystal chemistry of earth materials and the character of the SiO bonded interaction.

TRACE ELEMENT GEOCHEMISTRY OF MANTLE OLIVINE AND ITS APPLICATION TO GEOTHERMOMETRY

TRACE ELEMENT GEOCHEMISTRY OF MANTLE OLIVINE AND ITS APPLICATION TO GEOTHERMOMETRY

STRATIFORM CHROMITITES IN THE FARYAB OPHIOLITIC MASSIF, SOUTHERN IRAN

The Faryab ophiolitic massif, located in the extreme southernmost Iran, contains stratiform chromites in the ultramafic portion of its cumulate sequence. The stratiform chromites alternate with thick dunitic layers. Their Cr2O3 content varies between 42 and 44% and shows lower values compared to the disseminated chromites of the dunitic layers. Pyroxenites, websterites and wherlites cumulate layers alternate with dunites. Mg# of orthopyroxenes in websterites is higher than those in pyroxenites. Chromites in pyroxenites are relatively rich in Al2O3. The forsterite content of associated olivines varies between 88.5 and 90.5. The temperatures calculated from the chromite-olivine thermometer are very low, and vary from 654 to 710°C and corresponding probably to subsolidus reactions.

ULTRAHIGH-PRESSURE METAMORPHISM OF GARNET PERIDOTITES FROM POHORJE MTS. (EASTERN ALPS, SLOVENIA)

New evidence for ultrahigh-pressure metamorphism (UHPM) in the Eastern Alps is reported from garnet peridotites of Pohorje Mts. in Slovenia. In this area, an eo- Alpine UHPM has been recently documented in the eclogites (Janak et al. 2004). These eclogites are closely associated with metaultrabasites - predominantly serpentinised dunite and harzburgite with garnet peridotite remnants. The country rocks of eclogites and metaultrabasites are amphibolites, orthogneisses, paragneisses and micaschists. All these rocks belong to the Lower Central Austroalpine basement unit of the Eastern Alps, exposed in the proximity of the Periadriatic fault. Ultramafic rocks have experienced a complex metamorphic history. At least four stages of recrystallization have been identified in the garnet peridotite based on an analysis of reaction textures and mineral compositions. Stage I is a high-temperature protolith assemblage of olivine + orthopyroxene + clinopyroxene + Cr-spinel. Aluminous pyroxenes occur as inclusions in garnet, chromian spinel is preserved in the matrix. Stage II – an ultrahigh-pressure stage is defined by matrix assemblage garnet + olivine + orthopyroxene + clinopyroxene + Cr-spinel. Garnet contains up to 67 mol% of pyrope, olivine has 90 mol% of forsterite, orthopyroxene is low in Al2O3 (~0.8 wt%) and spinel has a Cr* ~ 50. Stage III – a decompression stage is manifested by formation of kelyphitic rims of high-Al orthopyroxene, aluminous spinel and pargasitic hornblende replacing garnet. Due to retrogression, garnet shows a decrease in MgO. Stage IV – is represented by formation of tremolitic amphibole, chlorite, serpentine and talc. P-T estimates based on geothermobarometric calculatios a) Fe-Mg exchange between garnet, olivine and orthopyroxene thermometers, b) the Al-in-orthopyroxene barometer indicate that the peak of metamorphism (stage II) occurred at ~820-900oC and 3-3.5 GPa. This is consistent with previous estimation of very high P-T conditions in metaultrabasites by Hinterlechner-Ravnik et al. (1991) and the associated eclogites (Janak et al. 2004). These results suggest that the mantle fragment (garnet peridotite) and the crustal fragment (eclogite) in the Pohorje Mts. both experienced a common UHPM during the Cretaceous orogeny. We propose that UHPM resulted from deep subduction of a continental slab which incorporated peridotites from an overlying mantle wedge.

Correction to “Effect of water on the spinel‐postspinel transformation in Mg2SiO4”

Correction to “Effect of water on the spinel‐postspinel transformation in Mg₂SiO₄”

Spinel refractory aggregates from natural raw materials

Utilization of the magnesium aluminate spinel in refractory applications is briefly reviewed. The synthesis of a magnesia aluminate spinel aggregate from natural raw materials is considered in terms of the crystal chemistry of the spinel structure and expected impurities. Principles for the formation of this spinel refractory aggregate from different natural raw materials are presented. The basic concepts were then applied to the reaction of a bauxitic clay with a natural magnesite. This combination of raw materials has the potential to produce a low-cost refractory aggregate that is a composite of spinel and forste rite. Experimental results are reported to produce a spinel refractory aggregate containing a small amount of forsterite. It possesses low apparent porosity and high bulk density suitable for industrial refractory applications, including steelmaking, aluminum and copper foundries and cement production.